This invention relates to the recovery of silver from photographic film. It has particular application to the recovery of silver from spent photographic film which is normally discarded.
In the normal processing (developing) of light-exposed photographic film, silver from the film coating enters into and is dissolved within the fixing solution used in the development process. It is desirable to reclaim such silver. It is also desirable to reclaim the silver from spent photographic film already developed, which has significant quantities of silver thereon. In the past it has been impractical to reclaim silver from used photographic film, especially since the most widely used method of recovering silver from scrap film is by the burning of the film base under controlled conditions and smelting the remaining ashes.
The present invention is directed to the reclaiming of silver derived from photographic film. A film processing unit is employed having a number of compartments through which the film is transported and containing fluids that act upon the constituents in the coating on the film. One of the compartments contains a fluid that includes a silver complex dissolved therein. In the case of spent photographic film, the processing unit is arranged to dissolve into solution the silver from the film, which is then removed from solution by a silver precipitating unit that includes anode-cathode elements connected to a source of electrical potential for depositing silver upon the elements. The precipitating unit is positioned within that compartment in which the silver complex is dissolved within the processing fluid. In the case of normal photographic development of light-exposed film, the precipitating unit is positioned within that compartment that contains the fixing solution used in the photographic process.
In this fashion, a soluble silver complex is precipitated out of solution to achieve the recovery of silver.
The invention will be more completely understood by reference to the following detailed description.